The present invention relates to a process for preparing an ultra-high molecular weight polyethylene and more particularly to a process for preparing an ultra-high molecular weight polyethylene superior in fluidity, free of fibril and easy soluble in a solvent by using a specific solid catalyst component and an organometallic compound.
Heretofore, for the preparation of an ultra-high molecular weight polyethylene, there have been known a number of processes each using a catalyst comprising as a carrier an inorganic magnesium compound such as magnesium halide, magnesium oxide or magnesium hydroxide and a transition metal compound such as titanium or vanadium compound supported on the carrier. However, these known processes involve various problems; for example, the resulting ultrahigh molecular weight polyethylene is generally low in bulk density and wide in particle size distribution and the particles thereof are fibrillated so difficult to dissolve in a solvent.
Further, in the production of an ultra-high molecular weight polyethylene fiber according to a gel spinning process which has recently been in increasing demand, it it absolutely necessary to provide an ultra-high molecular weight polyethylene which is easy to dissolve in a solvent and affords a homogeneous gel.
Thus, it has been desired to develop an ultra-high molecular weight polyethylene free of the above-mentioned problems.
It is an object of the present invention to solve the above-mentioned problems.
It is another object of the present invention to provide a process for preparing in high yield an ultra-high molecular weight polyethylene small in average particle size, narrow in particle size distribution, superior in free fluidity, free of fibrillated particles, easy to dissolve in a solvent and suitable for use in gel spinning.